The fundamental principles of complementarity and uncertainty are shown to be related to the possibility of joint unsharp measurements of pairs of noncommuting quantum observables. A new joint measurement scheme for complementary observables is proposed. The measured observables are represented as positive operator valued measures (POVMs), whose intrinsic fuzziness parameters are found to satisfy an intriguing pay-off relation reflecting the complementarity. At the same time, this relation represents an instance of a Heisenberg uncertainty relation for measurement imprecisions. A model-independent consideration show that this uncertainty relation is logically connected with the joint measurability of the POVMs in question. Ever since the inception of quantum mechanics, the principles of complementarity and uncertainty have been fundamental issues in the debate about an adequate understanding of this theory. Usually these principles are understood as expressions of limitations on the preparation and measurement of quantum systems; these limitations arise from the fact that in quantum mechanics there are many pairs of non-commuting observables. Complementarity is the mutual exclusiveness of preparing or measuring sharp values of certain pairs of non-commuting observables [1]. The uncertainty relation gives a more quantitative expression of complementarity: the more sharply the value of one quantity is defined or determined, the less sharply the other quantity can be defined or determined.Here we will develop a somewhat more positive view of the uncertainty relation: in one version, this relation can be understood as a pay-off inequality between the measurement imprecisions in joint unsharp measurements of a complementary pair of observables. This interpretation is introduced in Heisenberg's seminal paper of 1927 [2] but at that time and for many decades afterwards, it was not possible to formally distinguish it from the well-known relation for variances of sharp position and momentum, and thus it got conflated with this latter version.It was only after the introduction of positive operator valued measures (POVMs) into physics in the 1960s and 1970s (first by Ludwig and somewhat later by Davies, * Electronic address: p.busch@hull.ac.uk † Electronic address: c.r.shilladay@maths.hull.ac.ukHelstrom, Holevo, and others, for a survey, see [3]) that a notion of joint measurement of non-commuting observables could be formulated in the Hilbert space formalism of quantum mechanics. This has then been used to study models of joint measurement schemes for position and momentum, spin components and other quantities, which all led to some form of measurement uncertainty relation. This development is reviewed in [3]. In this letter we propose a new, realizable scheme of a joint measurement of complementary spin-1/2 components (or any pair of 'qubit' observables); we will find a novel pay-off relation for measures of unsharpness associated with the observables involved, and we will show that this form of Heisenberg measurement un...